The robust ghost pipefish (Solenostomus cyanopterus), also known as the blue-finned ghost pipefish, Racek's ghost pipefish, robust-snouted ghost pipefish or the squaretail ghost-pipefish, is a species of false pipefishes belonging to the family Solenostomidae.

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Solenostomus cyanopterus can reach a length of 17 cm (6.7 in)[2] and it is the largest of the ghost pipefishes. The body may be grey, brown, pink, yellow, or bright green, with small black and white dots.[2] This cryptic species looks very similar to a drifting piece of seagrass. The caudal fin may be truncated, rounded, or lanceolated; the caudal peduncle is quite short or absent. The pelvic fin is sexually dimorphic.[2] It is an uncommon species related to pipefishes and seahorses. It can be distinguished by the presence of the pelvic fins, the prominent spiny dorsal fin, and 27–35 star-shaped plates on the skin.

These fish float near motionlessly, with their mouths facing downwards, around a background that makes them nearly impossible to see. They feed on tiny crustaceans, sucked inside through their long snouts. They live in open waters except during breeding, when they find a coral reef or muddy bottom, changing color and shape to minimize visibility. Unlike true pipefish, female ghost pipefishes use their enlarged pelvic fins to brood their eggs until they hatch.

The robust ghost pipefish is mostly pelagic and reef-associated. When it settles on the substrate for breeding, it can be found on coastal reefs and weedy areas, at a depth of 2–25 m (6 ft 7 in–82 ft 0 in).[2]